1. Field of the Invention
The present invention relates to a method and apparatus for expanding a listening sweet spot using a virtual head related transfer function (HRTF).
2. Description of Related Art
Since there is a difference between two signals input into two ears due to original characteristics of a head transfer system of an individual, a listener can recognize a spatial cue of a sound source. Characteristic information about the difference between the two signals is contained in an HRTF. Therefore, 3D sound can be generated by adding spatial information to a simple sound using the HRTF.
The listener can enjoy the maximum 3D sound effect through a crosstalk cancellation process when positioned in a pre-defined listening sweet spot. The crosstalk cancellation process removes a sound mixing phenomena generated while sounds from a plurality of speakers are transferred to the listener's ears.
FIG. 1A shows a listener 1 positioned in a listening sweet spot. As illustrated in FIG. 1, when the listener 1 faces a position between two speakers S1 and S2, a listening sweet spot 3 is formed. When the listener 1 is positioned in the same distance from each of the two speakers S1 and S2, the listener 1 feels as if a virtual sound source 4 is located on the front axis 5 directly in front of the listener 1.
However, as illustrated in FIG. 1B, when the listener 1 moves to the left of the front axis 5, the listener 1 feels as if the virtual sound source is near the left speaker S1 and consequently deviates from the listening sweet spot 3. It can be consequently known that listen performance changes sensitively according to the relative position of the listener 1 to the listening sweet spot 3.
As described above, since the listening sweet spot is formed by a binaural synthesis system and a crosstalk cancellation system designed using the HRTF between the ears of a fixed listener and speakers at fixed positions, the listening sweet spot is very sensitive to the listener's movement.